Counterfeits of articles (for example, merchandise and garments), which are produced by copying the appearances of authentic articles, are being sold, and this cause problems. Under these circumstances, in order to ensure performance, reliability, and security of articles, and to maintain the value of the brands of articles, techniques for verifying authenticity of articles are required. As a technique for verifying the authenticity of the articles, a method of printing on articles with a special ink, and a method of affixing a chip having special optical reflection characteristics on articles, are known.
In the method using the special ink printed on an article, for example, a predetermined character or a figure is printed on an article by using an ink that fluoresces under ultraviolet light. When ultraviolet light is emitted on the article, the character or the figure becomes visible on the article, so that the authenticity of the article can be determined. For example, an ink having particles of a magnetic material or magnetized particles mixed therewith may be applied on an article, and the authenticity of the article can be verified by using magnetic sensors.
In a method using a chip having special optical reflection characteristics, a chip using optical characteristics of a cholesteric liquid crystal or a hologram formed thereon may be used. For example, this technique is disclosed in Japanese Unexamined Patent Applications Publication Nos. 63-51193 and 4-144796.
However, it is relatively easy to obtain inks similar to various special inks, and anticounterfeiting effects cannot be effectively obtained. Visual holograms, which are sophisticated counterfeits, are on the market, and the authenticity thereof is not easily determined by observation. Therefore, determination of the authenticity by only using a hologram is difficult. In view of the increasing sophistication of counterfeiting techniques, an identification medium using cholesteric liquid crystal, which cannot be easily counterfeited and which will provide a good discriminating ability, is required.